The red handfish (Thymichthys politus) is among Australia's most threatened marine fishes, with habitat degradation identified as one of the species' primary threats. Increased grazing pressure by the native shortspined sea urchin (Heliocidaris erythrogramma) can reduce macroalgal cover and habitat complexity at handfish sites, while declines in urchin populations in other regions are raising concerns regarding fishery availability of harvestable stocks. These contrasting challenges present an opportunity to align habitat restoration and fisheries objectives through translocation.
We evaluated the feasibility of relocating sub-legal shortspined sea urchins (<80 mm test diameter) from conservation-priority reefs to locally depleted commercial harvest grounds at three sites in eastern Tasmania. Urchins were diver-collected, transported and released across recipient sites spanning a range of habitat types. Alternative transport methods were tested to identify best practical release protocols. Changes in urchin density, retention and ecological responses at recipient sites were assessed following translocation.
Transport trials demonstrated that maintaining urchins in water throughout the relocation process resulted in the greatest vitality, although simpler methods using wet coverings also proved effective. Translocation significantly increased densities of undersized urchins at recipient sites, with retention highest in structurally complex boulder habitats. Post-translocation densities remained below grazing thresholds associated with barren formation, suggesting this approach can enhance future fishery resources without creating new habitat degradation risks.
Our results demonstrate that translocation may provide a practical alternative to culling, delivering dual benefits by protecting conservation-priority reefs from urchin overgrazing while supporting management of commercial fisheries stocks. By transforming an ecological threat into a fisheries resource, this approach offers a potentially scalable, nature-positive solution that aligns threatened species recovery with sustainable fisheries management. Future challenges include evaluating translocation as a tool to improve roe quality, plus development of governance and cross-sector partnerships among government, industry and researchers to enable implementation at larger spatial scales.